Flotation apparatus



W. E. GREENAWALT.

FLOTATION APPARATUS.

, APPUCATION FILED APR. 11. 1916. RENEWED MAY 3,1919.

1,350,605. Patented Aug. 24, 1920.

2 SHEETS-SHEET 1.

mT/VESSES 18 INYENTOR 17 w. E. GREENAWALT. FLOTATION APPARATUS. APPLICATION FILED APR. IZ, I9I6. RENEWED MAY 3, I919.

Patented Aug. 24, 1920.

2 SHEETSSHEET 2.

, larly effective in flotation operations.

PATENT OFFICE.

WILLIAM E. GREENAWAL'I, 0F DENVER, COLORADO.

FLOTAJTION APPARATUS.

Specification of Letters Patent.

Patented Aug. 24, 1920.

Application filed April 17, 1916, Serial No. 91,675. Renewed May 3, 1919. Serial No. 294,564.

To all whom it may concern:

Be it known that I, WILLIAM E. GREEN- AWALT, a citizen of the United States, residing in the city andcounty of Denver and State of Colorado, have invented certain new and useful Improvements in Flotation Apparatus, of which the following, is a specification.

My invention relates to apparatus for separating mineral values from their gangue by flotation, and more particularly to that class of apparatus inwhich liquids are impregnated with gases by rotary impregnators, as set forth in my pending applications, Serial No. 58,748, filed October 30, 1915, and Serial No. 68,718, filed December 27, 1915. It may also be regarded as a continuation in part thereon of my pending applications, Serial No. 812,951, filed J anuary 19, 1914, and Serial No. 845,011, filed June 13, 1914. In these applications, air, or any other gas, is introduced from a stationary source into a rotating perforated, or permeable,.hood, suspended within a tank containing a liquid, and submerged in the liquid, thus atomizing the gas in the liquid. This method of applying the gas is particiIit is most effective when the relative motion between the rotating impregnator, or hood, and the liquid is as great as possible. In the apparatus referred to, the best effect is obtained when the impregnator, or hood, rotates at a comparatively high speed while the liquid remains comparatively stationary or quiescent. It is also desirable to have the surface of the liquid as quiescent as possible, under the conditions, so that the mineral froth may be floated more efi'ectively, and a high grade of flotation concentrate obtained. In the applications above referred to means are shown to realize these conditions, but in the present application it is sought to realize them more perfectly and with greater facility.

The apparatus can best be described by referring to the accompanying drawings, in which Figure 1, represents a vertical section through the apparatus; Fi 2, a horizontal section on the line 22, ig. 1; and Fig. 3, a horizontal section on the'line 3-3, Fig. 1, part of the screens being omitted.

In the drawings, 1 represents a tank adapted to contain a liquid and the material to betreated. 2 is a hood, or impregnator,

suspended within the tank and submerged in the liquid, and having perforations 3, through which gases may pass from the inside of the hood to the liquid in the tank. 4 is a shaft rotating in the bearings 5, by means of which the hood 2 is suspended and rotated Within the tank when driven by the pulley 6. 7 is a feed hopper by means of which the material to be treated is fed into the tank through the pipe 37. This pipe preferably, passes through the side of the tank so as to deliver the material to be treated below the surface of the liquid, and in the vicinit of the rotating shaft. It is desirable to d eliver the materlal to be treated close to the shaft. The rotary motion of the liquid in the immediate vicinity of'the shaft will just about give the material the desired distribution. 8 is a pipe, preferably stationary, through which air or other gas may be delivered to the submerged hood, communicating with the source of gas supply through the pipe 9, and having a gas regulating valve 10. The pipe 8, preferably, enters the mouth of the hood and delivers the gas above the liquid in the hood, althrough, if the pipe is made lower and the liquid enters the pipe, no particular harm will be done, as it would again be expelled by the air or gas passing through the pipe. The pipe .8 may be omitted entirely and the gas delivered into the hopper 27 of the tank through the pipe 9, will of course, by its own buoyancy pass upwardly into the hood, much the same as through the pipe 8, but the arrangement of the pipe 8 is preferred. 11 is an opening in the bottom of the tank through which the gangue may be removed and wasted through the pipe 13. If desired, the material may be returned to the tank for retreatment through the pipes 12, 14, and 15, or passed on to another similar apparatus, for further treatment, through the pipe 16. Air or other gas is introduced into the pipe 14 through the pipe 17, thus making an air lift of the pipe 14. Clogging in the opening 11, in the bottom of tank 1, is removed or prevented by an air or water jet introduced through the pipe 18. 19 is a launder into which the mineral froth 21 may overflow and be removed from the tank and delivered into the trough 20. 22 is a feed'pipefor the fresh ore delivered to the hopper 7 to be introduced into the tank for treatment. 24 is a casing surrounding the hood to which are attached bafiies 23, the inner edges of which are brought in close proximity to the periphery of the hood. The casing 24, with the bafiles 23, rests on the horizontal support 28, which, in turn, is supported by the conical sides of the tank. The support for the casing is preferably in the shape of a spider, and having a the sides of the tank, which is more quiescent than the space within the casing, in which the hood 2 rotates. This arrangement allows the coarser ground ore to pass over the hood and through between the baffies into the hopper 27, while the finer ore, or slimes may pass through the more quiescent space 26 to the hopper 27. The lips 34, on the casings, serve to hold the screens in place and also prevent the liquid in the space 26 from becoming unduly agitated, b currents passing through the screen. his construction makes the bafl'ling arrangement independent of the sides of the tank and easily inserted and removed. 35 is a water pipe over the launder 19, by means of which jets of water wash the mineral froth from the overflow launder 19 to the launder 20 which conveys the froth awa fromthe apparatus. The hood 2 is pre erably constructed with a multiplicity of small holes in the top and periphery through which the gas passes into the liquid. The speed of rotation of the hood may vary from several hundred to several thousand revolutions per minute, depending upon the size of the hood, the material to be treated, and the results desired. The screens 25, 25 and 25", are rather coarse: 3-mesh has been found to give good results.

The apparatus is assembled and dismantled with considerable facility. In assembling the apparatus, the supports 28, are first fitted into the conical bottom of the tank. The casing 24, with the baffles 23, is then placed in position, on the supports 28. The hood .2, and shaft 4, are then lowered, and the hood properly adjusted in reference to the casing 24 and the bafiles 23. The screen 25 is then placed on top of the casing and baflles, which support the screen. Casing 30 with its bafiles 31, and its corresponding screen 25*, is then placed in position, and so on for the number of casings and baffles desired. For small machines the casings will usually be made in halves and bolted together in place; for large machines the easings will usually be made in four quarters and bolted together in place. In this way the casings and baffles are easily inserted and removed without necessarily interfering with the hood, or impregnator. The number of casings and bafiles used is a matter of experiment and discretion for each particular ore, as also the number and mesh of the screens, although the mesh of the screens should never be so fine as to revent the free flow of pulp 'and gases t rough them.

In operating the apparatus, the tank 1 is filled with liquid and the material to be treated, which may be assumed to be a floatable ore pulp ground to, say, 80 mesh. The shaft and hood are then rapidly rotated, at, say, from 100 to 1000 revolutions per minute, driven by the pulley 6. The air, or gas, valve 10 is then opened and the gas introduced into the hood through the pipe 9 and stationary pipe 8, and-its amount is regulated so as not to be in excess of that capable of passing through the perforations 3, in the hood 2. There is no mechanical connection between the rotating hood 2, and the stationary gas delivery pipe 8, so that the hood can conveniently be rotated at any speed desired. The gas, in passing through the perforations of the rapidly rotating.

hood, is atomized in contact with the liquid, and the atomized gas, in passing through the liquid having the finely ground ore in suspension, floats the mineral particles to the surface, while the gangue passes downwardly into the hopper 27. The heavier particles of gangue pass downwardly within the casings and between the baffles and through the screens, and over the surface of the rotating hood, while the gangue slimes will 'passdownwardly through the more quiescent space 26, between the casing and the tank. The amount of separation between the sands and the slimes manifestly depends upon the number or height, of the casings. In this way, the apparatus may also act as a classifier, .or pulp thickener, and once the most desirable upwardly I i gravity of the pulp having been determined by adjusting the number of casings, this condition can always be maintained, no matter what the proportion of solid to liquid is on entering the apparatus. The slimes and sands, although somewhat separated during treatment, are again brought together in the hopper 27, below the casing support 28, and are drawn from the hopper through the opening 11, and may be wasted through the pipe 13, or returned for re-treatment through the pipes 12 and 14, into the same apparatus throughthe pipe 15, or a similar apparatus through the pipe 16. The mineral froth 21, rises to the surface and overflows into the launder 19. It may be assisted toward the periphery of the tank by a vane 38, attached to the rapidly rotating shaft, which creates an air current and forces the froth outwardly. The froth is broken up and washed out of the launder 19, by water-jets from the pipe 35, placed directly over the launder. The jets of water ,washes the froth into the trough from whence it may be conveyed where desired.

The efliciency of this apparatus, as an atomizer of the gas, and consequently as a floater, can easily be realized by the following considerations. Assuming a hood 36 inches in diameter, having peripheral perforations of inch, and a'rotary speed of 1000 revolutions per minute, it follows that since the lineal speed of the periphery is about 9425 feet per minute, that the gas, escaping through the g g perforation, is distributed through 9425 feet of the liquid, and hence,must be thoroughly atomized, and distributed through the liquid. The perforations, being considerably larger than the finely ground ore, cannot become clogged,

and the passage of the gas through theper forations prevents clogging also, so the apparatus works under uniform conditions until either the hood or the casing is badly worn.

The ore pulp, or material to be treated, is preferably introduced through a pipe 37 submerged in the liquid, just below the froth. This leaves the surface of the tank entirely free and facilitates the removal of the froth from the surface of the liquid.

The thickening of the pulp in the apparatus may be accomplished either by the speed of rotation of the hood and the amount of air introduced into the liquid through the hood, or by the height and number of sections of the casing, assisted by the screens: Usually all these factors will be operative at the same time. The coarser material, or sands, passes through a more thoroughly aerated portion of the apparatus than the fines, or slimes, so that the treatment -of both sands and slimes is pretty well balanced.

The spider support for the casing and baflles, as shown by 28 in Figs. 1 and 2, is a convenient arrangement. The pipe 8, passes up through the center, and delivers the air to the hood, while the arms of the spider support the casing, and the space between the arms allows both the sands and the slimes to pass into the hopper 27. The arms also act to retard the circulatory motion of the liquid in the hopper, below the impregnator.

The speed of rotation, the amount of air, and the size of the gas passages, will depend largely .on the results desired, and largely also on the size of the apparatus. A large hood, must of necessity, be rotated quite slowly, while a very small hood should be rotated quite rapidly. A high rotary speed, with a comparatively small amount of air, appears to give a cleaner separation, while a large amount of air appears to give a greater capacity than a small amount of am I claim:

1. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid, means for introducing a gas into the tank, rotary means suspended within the tank and submerged in the liquid for impregnating the liquid with the gas, baflles arranged about the impregnator to retard the circulatory motion of the liquid, supports for the baflles below the impregnator and arranged to allow the gangue to pass beneath the baffle supports, and means for withdrawing the gangue from below the baflle supports.

2. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid, means for introducing a gas into the liquid, rotary means suspended within the tank and submerged in the liquid for impregnating the liquid with the gas, baflles arranged about the impregnator to retard the circulatory motion of the liquid and allow the gan ue to pass downwardly be tween the ba es, supports for the baffles below the impregnator and arranged to allow the gan ue to pass downwardly beneath the ba e supports, a hopper below the baffle supports, and means for withdrawing the gangue from the hopper.

3. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid, means for introducing a gas into the tank with which to impregnate the liquid, rotary means for impregnating the liquid with the gas, baffles and a sectional casing arranged about the periphery of the impregnator, and separate baflies and sectional casings arranged above the upper surface of the impregnator.

4. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a gas into the tank, means for impregnating the liquid with the gas, baflies arranged about the impregnator, and a casing to which the baffles are attached arranged in horizontal ections.

5. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a gas into the tank, means for impregnating the liquid with the gas, baflles arranged about the impregnator, and a casing to which the baflies are attached arranged in horizontal sections.

6. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a liquid into the tank, means for impregnating the liquid llquld wlth a gas, a gangue with the gas a casing'interposed between the impregnator and the sides of the tank, and baflles projecting inwardly attached to the casing.

7. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a' liquid and the material to be treated, means for introducing a'gas into the tank, means for impregnating the liquid with the gas, a'casing arranged in horizontal sections interposed between the impregnator and sides of the tank, and a screen inserted between the horizontal sections of the casing.

8. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a gas into the tank, means for impregnating the liquid with the gas, and a casing arranged between the impregnator and sides of the tank so as to allow the sands to pass downwardly between the impregnator and the casing and the slimes to pass downwardly in the more quiescent space between the casing and sides of the tank.

9. In apparatus for separating minerals from their gangue by flotation, a tank adapted tocontain a liquid and the material to be treated, means for im regnating the hopper in connection with the tank, means for introducing the material to be treated into the tank and into the liquid, and means arranged so as to provide separate channels for the sands and the slimes to the gangue hopper.

10. In apparatus for/separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a gas into the tank, means for impregnating the liquid with the gas, a casing arranged between the impregnator and sides of the tank so as to allow the sands to pass downwardly between the impregnator and the casing and the slimes to pass downwardly in the more quiescent space between the casing and sides of the tank, and means having a submerged opening for delivering the material to be treated in the vicinity of the center of'the tank and within the casing.

11. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain the liquid and the material to be treated, means for impregnating the liquid with a gas, a casing with baffles attached thereto surrounding the impregnator, and a spider support for the casing having arms located below the impregnator.

12. An apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, means for introducing a gas into the tank, means for impregnating the liquid with the gas, superimposed casings with baflles attached arranged-about the impregnator, screens interposed between the casings, and lips attached to the casings covspace between the casing and sides of the tank.

14. In apparatus for separating minerals from their gangue by flotation, a tank adapted to contain a liquid and the material to be treated, a rotary impregnator having gas passages suspended within the tank and submerged in the liquid, meansfor causing a flow of gas through the gas passages of the rotary mpreg'nator, a casing interposed between the impregnator and the sides of the tank so as to form a passage for the liquid communicating with the upper portion'and with the lower-portion of the tank, and means for rotating the impregnator about its vertical axis as the center of rotation.

WILLIAM E. GREENAWALT. Witnesses:

.IVA LEONA MYERS,

FRED'L. Soo'r'r. 

